The present invention relates to an automatic installation for the heat treatment of workpieces in fluidized beds.
Methods and installations for improving heat exchanges between a fluidized bed of solid particles and workpieces to be treated are already known through the French Pat. No. 70 21 613, filed on June 12, 1970, and its Addition No. 71 19 245, filed on May 27, 1971, which consist in maintaining the workpieces in an open-top vessel comprising a bottom structure adapted to retain the workpieces, while permitting the passage of the fluidized particles, and immerging this vessel into the fluidized bed, whereby an upward circulation of the fluidized particles takes place within the vessel through the workpieces to be treated, such that the deeper the immersion of said vessel into the fluidized bed, the stronger the circulation of fluidized particles.
When carrying out this method, a problem arises when introducing and retracting the workpieces to and from the fluidized bed. Two solutions have been proposed to cope with this problem:
In the first solution, in the case of a discontinuous operation, the workpieces to be treated are disposed in containers or wire-racks which are subsequently immersed into the fluidized bed; and,
In the second solution, permitting an automatic and continuous operation, the workpieces are disposed in wire-racks and transported by means of an elevator capable of immersing and extracting the wire-racks into and from the fluidized bed, the elevator station comprising horizontal beams along which trolleys or like carriers supporting the wire-rack gripping means are adapted to travel. A typical example of an automatic installation of this character is disclosed in the French Pat. No. 79 02 967, filed on Feb. 6, 1979, by the same applicant.
The first solution is objectionable, in that it permits only a discontinuous operation, with separate and successive charges, and the second solution is awkward, in that mechanical parts are handled in the fluidized bed and that the installation necessary therefor has excessive overall dimensions.